1. Field of the Invention
The present invention relates to an electrophotographic printing apparatus such as a laser beam printer or a copier.
2. Description of the Related Art
JP-A-2003-160262 discloses a laser beam printer including a sheet transport mechanism that has a sheet meander correction mechanism that corrects a meander of a print sheet.
In a case where a backlash arises as a result of abrasion, or the like, of a drive section gear of the sheet meander correction mechanism, even when an amount of drive of a motor computed by a microprocessor is output to a motor drive circuit in order to correct the meander, a pressure roller sometimes fails to move correctly by an amount corresponding to the backlash of the gear. Because of this failure, positional data pertaining to the pressure roller managed by the microprocessor do not coincide with the real position of the pressure roller. When transport of the sheets is continued in this state, a single correction made on the meander corresponds to the amount of backlash of the drive section gear. Hence, no problems arise in corrections on the meander of a sheet or a transport of a sheet. However, when the corrections are performed repeatedly, an error between the positional data pertaining to the pressure roller managed by the microprocessor and the real position of the pressure roller by the backlash is accumulated. Eventually, the position of the pressure roller moves to a location where a fixing failure occurs, and there arises a case where the pressure roller detection unit detects an error. Even in the case of the motor of the drive section of the sheet meander correction mechanism temporarily looses synchronization, the positional data pertaining to the pressure roller managed by the microprocessor do not coincide with the actual position of the pressure roller, and there arises a case where an error is erroneously detected.